Doctrine of signatures

Eyebright was used for eye infections, from the supposed resemblance of the flower to an eye

The doctrine of signatures, dating from the time of Dioscurides and Galen, states that herbs that resemble various parts of the body can be used by herbalists to treat ailments of those parts of the body. A theological justification for this, as stated by botanists like William Coles, was that God would have wanted to show men what plants would be useful for.

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Paracelsus (1491–1541) developed the concept, writing that "Nature marks each growth ... according to its curative benefit",[1] and it was followed by Giambattista della Porta in his Phytognomonica (1588).

The writings of Jakob Böhme (1575–1624) spread the doctrine of signatures. He suggested that God marked objects with a sign, or "signature", for their purpose.[2] Plants bearing parts that resembled human body-parts, animals, or other objects were thought to have useful relevance to those parts, animals or objects. The "signature" could sometimes also be identified in the environments or specific sites in which plants grew. Böhme's 1621 book The Signature of All Things gave its name to the doctrine.[1]

The botanistWilliam Coles (1626–1662) supposed that God had made 'Herbes for the use of men, and hath given them particular Signatures, whereby a man may read ... the use of them.'[1] Coles's The Art of Simpling and Adam in Eden, stated that walnuts were good for curing head ailments because in his opinion, "they Have the perfect Signatures of the Head". Regarding Hypericum, he wrote, "The little holes whereof the leaves of Saint Johns wort are full, doe resemble all the pores of the skin and therefore it is profitable for all hurts and wounds that can happen thereunto."[2]

A theological justification was made for this philosophy: "It was reasoned that the Almighty must have set his sign upon the various means of curing disease which he provided".[3]

For the late medieval viewer, the natural world was vibrant with images of the Deity: 'as above, so below,' a Hermetic principle expressed as the relationship between macrocosm and microcosm; the principle is rendered sicut in terra. Michel Foucault expressed the wider usage of the doctrine of signatures, which rendered allegory more real and more cogent than it appears to a modern eye:

Up to the end of the sixteenth century, resemblance played a constructive role in the knowledge of Western culture. It was resemblance that largely guided exegesis and the interpretation of texts; it was resemblance that organized the play of symbols, made possible knowledge of things visible and invisible, and controlled the art of representing them." (The Order of Things , p. 17)

The phrase "signatures of all things" appears in the beginning of episode 3 in James Joyce's novel Ulysses. The character Stephen Dedalus walking along the beach, thinking to himself "Signatures of all things I am here to read, seaspawn and seawrack, the nearing tide, that rusty boot."

The signatures are described as post hoc attributions and mnemonics,[8] of value only in creating a system for remembering actions attributed to medical herbs. There is no scientific evidence that plant shapes and colors help in the discovery of medical uses of plants.[8] However, once a medicinal use has been discovered for a particular plant, selective propagation could lead to a resemblance between the herb and the organ system it treats; in Traditional Chinese Medicine, ginseng root's value is largely determined by its resemblance to the human form. Thus, ginseng with a propensity for taking such a shape has been preferentially propagated for thousands of years. In this way, it could be argued that such superstition is practically self-fulfilling, and that the observed similarities are indeed "signatures"—not of the plant's creator, but of its caretakers.

Additionally, colorful phenols such as lycopene can inhibit the formation of Advanced glycation end-products in vivo, potentially linking a plant tissue's color to the potency of its health-promoting effects.[9]

^Irvine, Alexander (1860). The Phytologist: A Botanical Journal, Volume 4. William Pamplin. p. 308. As late as 1657 we find William Coles, who was a herbarist ... speaking of Spleenwort, or Miltwort, tells us that the learned Crollius, amongst the signatures of parts, doth set down Ceterach to have the signature of the spleen, and that therefore it is profitable for all diseases thereof;